Phosphorus (P) is a macroelement primarily found in insoluble forms in nature. Enhancing the effectiveness of P is crucial for sustainable agricultural development and ecosystems. The research employed a combination of sequential extraction methods, high-throughput sequencing techniques, microbial culturing, and ecological network analysis of bacterial communities, along with module comparison, to explore the dynamics of different P fractions in calcareous soils. The objective of incorporating biochar into the composting of maize stover and cattle dung was to uncover potential microbial processes that could facilitate the activation of inorganic non-labile P. Findings revealed that during the composting process with biochar, bacterial populations played three distinct roles in the transformation of inorganic non-labile P compounds (such as occluded P and Ca